Fluorescent agents and process of



United States Patent FLUORESCENT AGENTS AND PROCESS OF MAKING T HE SAME James W. Libby, l ra, Dexter B. Pattison, and Frithiof Zwiigmeyer, New Castle County, DelL, assignors to E. 1. tin Pont de Nemours & Company, Wilmington, DeL, a corporation of Delaware No Drawing. Application October 31, 1952, Serial No. 318,106

7 Claims. (Cl. 260-2411) This invention relates to novel organic compounds.

More particularly, this invention deals with novel compounds which correspond to the general formula Rs L l SOiN CHZOHZ /O CHzCHa which completes with the N-atom a morpholine ring; R4. and R5 individually represent hydrogen, alkyl or hydroxyalkyl, or jointly represent the oxydiethylene radical above indicated.

it is an object of this invention to produce fluorescent agents having good affinity for nylon fiber, moderate to good affinity for cotton fiber, and good resistance to bleach. Various additional objects and achievements of this invention will appear as the description proceeds.

So called optical bleaching agents for cotton have been known for some time. They are generally watersoluble compounds having a natural aflinity for cotton, and are applied thereto from aqueous solution, in a manner similar to the application of dyes. The action of the ultra-violet wave lengths present in daylight then excites a bluish fluorescence in the dyed fiber, which overcomes any natural yellowishness in the fiber and gives the latter a brilliant-white appearance.

To be applicable also to hydrophobic fiber, for instance nylon or cellulose acetate, it is essential that the fluorescent dye be free of water-solubilizing groups, such as sulfo or carboxy. Thus, the requirements of affinity for hydrophobic fiber and aflinity for cotton are in a sense incompatible.

It has also been known that whereas 2-p-aminophenylbenzothiazoles in general have aflinity for the one fiber or the other and act thereon as optical bleaching agents, many compounds of this series turn yellow upon the fiber if the latter is treated with chemical bleaching agents, such as sodium hypochlorite. This of course would defeat the very purpose of treating the fiber with the optical bleaching agent.

We have now discovered that compounds of the general formula hereinabove have good affinity for nylon fiber, moderate to good affinity for cotton fiber and good resistance to bleach, in that they will not turn yellow when treated with sodium hypochlorite. The aflinity for cotton a 2,733,242 Patented Jan. 31, 1956 will generally be greater the less the molecular weight of the compound. Accordingly, the preferred compounds for the purpose of this invention are those compounds of the above general formula in which the sum of the carbon atoms in R1, R2, R3, R4 and R5 does not exceed 10.

Some individual members of this group have various additional desirable properties. For instance, those subjected by us to dermatological tests have been found to be non-toxic and safe in this respect.

Accordingly, our invention opens up a new field in the art of whitening nylon or cellulose acetate with optical bleaching agents.

The preparation of our novel compounds may follow several distinct procedures, of which the following are typical:

1. Chlorosulfonylation of an unsulfonated p-dimethylaminophenyl-benzothiazole compound, followed by amidation.

2. Chlorination of a sulfonated p-dimethylaminophenylbenzothiazole to convert the SOsH group into SOzCl, followedby amidation.

3. Synthesis from a p-dialkylamino-benzaldehyde and an ortho-amino-phenyl mercaptain which already possesses a sulfonamide group.

4. Chlorosulfonylation of a p-acetylaminophenyl-benzothiazole, followed by amidation in the SOzCl group, hydrolysis of the acetyl group, and alkylation in the pamino N-atom.

Without limiting our invention, the following examples will serve to illustrate our preferred embodiments thereof. Parts mentioned are by weight.

EXAMPLE 1 Fifty parts of N,N-dirnethyl-dehydrothio-p-toluidine (prepared by methylation of dehydrothio-p-toluidine with methanol and HCl by well known methods) were added to 350 parts of chlorosulfonic acid below 8 C. and the mixture was heated three hours at C. After cooling, the reaction mixture was added to ice and water below 5 C. The acid chloride was filtered off, washed with ice water, and divided into three equal portions. One of these portions was added to 90 parts of 27% ammonia below 10 C. and stirred overnight at 25 C. After acidification with hydrochloric acid, the N,N-dimethyldehydrothio-p-toluidine sulfonamide was isolated by filtration, washed with water, and dried.

The other two portions were likewise treated, respectively, with monomethylamine in methyl alcohol solution and with monoethanolamine in ethyl alcohol, to yield the N-methyl and the N-hydroxyethyl sulfonamides.

Properties of the three compounds obtained are tabulated below. The melting points were taken after recrystallization from cellosolve.

General formula All three sulfonamides are powerful whitening, agents for textile fibers. When dimethyldehydrothio-p-toluidine sulfonamide is applied to cotton from a detergent bath it is approximately equal in whitening power to the best whitening agents now on the market. In addition, dimethyldehydrothio-p-toluidine sulfonamide, in small quantities, is an effective whitening agent for nylon, silk, cellulose acetate, and wool.

EXAMPLE 2 A mixture of 25 grams of 2(p-dimethylaminophenyl)- benzothiazole and 100 cc. of chlorosulfonic acid was heated four hours at 100 C., 2 hours at 120 C., and three hours at 150 C., until a spot test showed nearly complete solubility in dilute aqueous alkali. The charge was cooled, and drowned in ice and water below C. The acid chloride was filtered off, washed with ice water, and stirred overnight with ammonia. After acidification, the product was filtered off, washed and dried. Recrystallization from ethylene-glycol-monoethyl ether gave 2 (p dimethylaminophenyl) benzothiazole sulfonamide, which had a melting point of 279-282 C. This compound was apowerful whitening agent for textile fibers.

The initial intermediate required for this example is a known compound. See, for instance, Bogert and Taylor, Chem. Abst., vol. 26, p. 1281.

EXAMPLE 3 A mixture of 77 grams of 2-(p-dimethylaminophenyl)- benzothiazole sulfonic acid and 200 cc. of chlorosulfonic acid was heated 2 hours at 9095 C. The reaction mass was then cooled to 24 C. and drowned in ice. The sulfonic acid chloride was filtered and washed nearly acid-free with ice water. The wet filter cake was agitated over night at room temperature with a large excess of 27% aqueous ammonia. The sulfonarnide slurry was then acidified with hydrochloric acid and filtered, after which the 2-(p-dimethylaminophenyl)- benzothiazole sulfonamide was washed thoroughly with water and dried. The product appeared to be identical with that obtained in Example 2.

By reacting, similarly, the 2-(p-dimethylaminophenyl)- benzothiazole sulfonyl chloride with aqueous methylamine and ethanolamine dissolved in ethanol, the corresponding N-methyl and N-hydroxyethyl sulfonamides were obtained.

All of these sulfonamides are powerful whitening agents for nylon, cellulose acetate, wool and cotton.

The initial material for this example was prepared by drying the free monosulfonic acid filter cake obtained according to Example 1 of co-pending application of F. Zwilgmeyer,. Serial No. 299,260 (Patent No. 2,715,- 629, issued August 16, 1955).

EXAMPLE 4 Step 1.-A mixture of 118 grams of 4-chloro-3-nitrobenzenesulfonamide and 472 cc. of ethylene-glycol monoethyl ether was heated to 100 C., and a sodium disulfide solution, made from 62.5 grams of sodium sulfide crystals, 8.3 grams of sulfur, and 60 cc. of water was added at 90100 C. After heating three hours at 90-95 C., the solid was separated by hot filtration, Washed with water, and dried. It constituted 2,2-dinitrodiphenyldisulfide-4,4'-disulfonamide.

Step 2.A mixture of 60 grams of the diphenyldisulfide obtained in Step 1, 116 grams of sodium sulfide crystals, and 400 cc. of water was heated at reflux for four hours, and acidified with hydrochloric acid until barely acid to Congo red paper. The 3-amino-4-mercaptobenzenesulfonamide was filtered off, washed with NaCl solution, and dried.

Step 3.A mixture of 25.5 grams of the 3-amino-4- mercaptobenzenesulfonamide obtained above, 3.2 grams of sulfur, 13.7 grams of p-dimethylaminobenzaldehyde, and 60 cc. of o-dichlorobenzene was agitated and heated one half hour at 140-160 C. After cooling, the product was filtered off and washed with alcohol. Recrystallization from ethylene-glycol-monoethyl ether gave light yellow crystals of 2-(p-dimethylaminophenyDbenzothiazole-S-sulfonamide having a melting point of 292- 294 C. This compound is a good whitening agent for nylon, cellulose acetate, and cotton.

The successive reactions involved in the above procedure may be summarized as follows:

mums No,

H.N.o.s No, on: S0,.NH1

mums 3 NH,

s\ HN.O2S N/ The final product is apparently an isomer of that obtained in Examples 2 and 3.

EXAMPLE 5 Ten parts of 2-(4'-morpholinyl-phenyl)-benzothiazole (prepared by first reacting N-phenyl morpholine with POCls and formamide according to U. S. P. 2,558,285, followed by heating the resulting p-morpholinyl-benzaldehyde with an equimolecular amount of o-aminothiophenol, in the presence of l-atom equivalent of sulfur at 170 C. for 2 hours) were added to 180 parts of chlorosulfonic acid at 0-8 C. and then heated at C. for 3 hours. The ehlorsulfonation mass was then cooled and drowned below 5 C. in iced water. The precipitated sulfonchloride was filtered and washed with ice water until nearly acid-free. The filter cake was added to parts of 20% aqueous dimethylamine solution at 0 C. and agitated for 16 hours allowing the temperature to rise to 25 C. The reaction mass was then neutralized with hydrochloric acid, filtered, and the product Washed with water and dried. The product is a nearly white solid, having presumably the formula c N o S OzN s EXAMPLE 6 Twenty parts of 2-(4-dimethylaminophenyl)-6-methylbenzothiazole were added to 143 parts of chlorosulfonic acid with agitation at 010 C. The mixture was then heated slowly to 130 C. and held at that temperature for 1 hour. The reaction mass was then cooled to room temperature and drowned in ice. The yellowish product which separated was filtered off and added to a mixture of 60 parts of diethylamine and parts of ethanol at 010 C. After stirring at this temperature for two hours, the mixture was slowly brought, with stirring, to room temperature. The cream colored product was filtered oif, slurried in a mixture of 20 parts of sodium carbonate in 200 parts of water, and again filtered off. It was then slurried in 100 parts of ethanol, again filtered off, and dried at 75 C.

The 2 (4' dimethylaminophenyD-6-methyl-benzothiazole diethylsulfonamide thus obtained was soluble in EXAMPLE 7 Example 6 was repeated except that the solid product resulting from drowning the first reaction mass in ice was filtered ofl and added to a mixture of 80 parts of morpholine and 160 parts of ethanol at 0-10 C. After stirring for two hours at 0-l0 C., the mixture was agitated over night and allowed to warm up to room temperature. The resultant cream colored product was filtered oif and purified from aqueous sodium carbonate, then ethanol, and dried as described in Example 6.

2 (4 dimethylamine phenyl 6 methyl benzothiazole morpholinyl sulfonamide was thus obtained, whose solutions in alcohol or acetone exhibited an intense bluish-white fluorescence when exposed to ultra-violet radiation.

EXAMPLE 8 20 parts of 2 (4 dimethylaminophenyl) 6 methyl benzothiazole was treated with 143 parts of chlorosulfonic acid as in Example 6. The reaction product was cooled to room temperature, then drowned in ice. The resulting solid product was filtered off, and added to a mixture of 200 parts of ethanol and 105 parts of diethanolamine at 0-l0 C. The mixture was stirred for two hours at O-l0 C., then allowed slowly, with stirring, to rise to 2025 C. The cream colored 2-(4'-dimethylaminophenyl)-6-methyl benzothiazole diethanol sulfonamide was filtered off, purified by slurrying in sodium carbonate and alcohol as in Example 6, and dried at 75 C. Solutions of the product in alcohol or acetone exhibited an intense bluish-white fluorescence when exposed to ultraviolet radiation.

The following additional example describes a method for using the aforegoing Whitening agents.

EXAMPLE 9 Soap containing 0.02% of the Z-(p-dimethylaminophenyl)-G-methyl benzothiazole sulfonamide of Example 1 was prepared by mixing 60 grams of a neutral fatty acid soap and 100 cc. of water in a colloid mill until a smooth slurry was obtained, followed by'the incorporation of a solution of 0.012 grams of said whitening agent in 60 cc. of methanol and thereafter drying the mixture on a rotary drum drier at 100 C. The soap flakes thus obtained were ground to 40 mesh. The resulting soap powder showed an intense whitish-blue fluorescence when exposed to ultra-violet light.

A dye bath was made by dissolving 0.4 gram of the treated soap in 100 cc. of Water at 130 F. A 2 gram piece of cloth was dyed in this bath by conventional methods, and dried. Nylon, cellulose acetate, and cotton cloths dyed in this fashion were considerably whiter than untreated control samples.

In manners similar to the above examples, various other compounds within the scope of this invention may be readily prepared. In particular, the p-dimethylaminophenyl-benzothiazoles where mentioned in the above examples, may be replaced by the corresponding p-diethylamino-, p-(ethyl-methylamino)- or other lower p--dialkylamino-phenyl derivatives of benzothiazole and 6 methyl benzothiazole. The monosulfo p (dimethylamine-phenyl)-benzothiazole of Example 3 may be replaced by the corresponding p-diethylamino-, or p-ethylmethylamino-phenyl derivatives of Zwilgmeyers copending application above identified.

The amine for amidation of the SOzCl group in the several examples above may be ammonia, monomethylamine, monoethylamine, monoethanolamine, dimethylamine, ethylmethylamine, diethylamine, diethanolamine, monomethyl-monoethanolamine, monoethyl-monoethanolamine, or morpholine. Or, one may start with a corresponding sulfonamido-3-nitro-4-chloro-benzene as in Example 4, and condense the thiazole following Step 2 with an optional p-dialkylamino-benzaldehyde in which the alkyl groups possess l to 4 C-atoms each.

Compounds having hydroxyethyl groups in the p-amino N-atom are best prepared by the method indicated under the numeral 4 in the above general discussion. For instance, N-acetyl-dehydrothioparatoluidine (made by acetylation of dehydrothioparatoluidine) is reacted with chlorosulfonic acid and then with dimethylamine as in Example 1, to give N-acetyl-dehydrothioparatoluidine sulfone-dirnethylamide. The acetyl group is then hydrolyzed ofi by the aid of dilute mineral acid, and the resulting primary amine is reacted with ethylene oxide in an autoclave to give the corresponding di(hydroxyethyl) compound.

Numerous other variations in the details of procedure will be readily apparent to those skilled in the art.

We claim as our invention:

1. A compound of the general formula S R1- R2 Ra L l I R4 SO2N wherein R1 represents a member of the group consisting of hydrogen and methyl, the grouping represents a radical of the group consisting of dialkylamino, monoalkyl-mono(hydroxyalkyl)-amino, di(hydroxyalkyl)amino and morpholino, while the grouping represents a radical of the group consisting of primary amino, monoalkylamino, dialkylamino, mono(hydroxyalkyl)arnino, monoalkyl-mono(hydroxyalkyl)amino, di- (hydroxyalkyl)amino and morpholino, all the alkyl radicals being radicals of not more than 4 C-atoms each, and

wherein R1 represents a member of the group consisting of hydrogen and methyl, while the grouping represents a radical of the group consisting of dialkylamino, monoalkyl-mono (hydroxyalkyl)amino, di(hydroxyalkyl)amino and morpholino, and then reacting the inter- 8 mediate chiorosulfonyl compound thus produced with a dehydrothio-p-to1uidine, and then reacting the resulting base selected from the group consisting of ammonia, chlorosulfonyl compound with ammonia, whereby to conmonoalkyl and dialkyi amines, mono(hydroxyalkyl) vert the same into the corresponding sulfonamide.

amines, monoalkyl-mono(hydroxyaikyi) amines, di(hydroxyaikyl) amines and morphoiine, all the alkyl radicals eferences Cited in the file of this patent aforementioned being radicals of not more than 4 C-atoms UNITED STATES PATENTS each.

7. A process of producing a fluorescent agent, which g f s comprises reacting chlorosulfonic acid with N,N-dirnethy1- e ay 1 

1. A COMPOUND OF THE GENERAL FORMULA 